Saizer

Ok I bought an 89 ex cab with a 3.0 and automatic in it and she wants to run hot. I know they are prone to HG's but I do not think thats the issue. Here is why.
Bought the truck yesterday and it sounds like it runs pretty good (it is popping a code 25) but not idling rough. The previous owner wasn't driving it much but did say it liked to run warm.
We did pressure test the coolant system first time pumped it up to 15 PSI and it dropped to around 11PSI in 20 mins. Which I know is not great. Just to make sure we pumped it up again but to like 25PSI thinking increased pressure it would drop quicker right well didn't drop at all in 5 mins and actually was pushing the upper raditor hose off. Seemed like an ok sign so bought the truck.
So jump on the highway truck seems to be running great needle is running less then half for about 35 miles then we hit a few hills and the temp spikes all the way to hot. We were given an extra thermostat from the previous owner so we run too town grab a bucket and coolant and change the thermostat on the side of the road. Back on the highway again truck is now running a under half on the temperature for about a hour on the highway. Started climbing some hills and by the second one she moved all the way to hot again. Pulled over let it cool down again then started for home again, the rest of the trip (about an 1.5 hours on the highway) went ok but it was flat ground. The needle was in the middle or under the rest of the drive however when slowing down in the small towns is when the needle would move toward the right and I mean rather quickly and when I got home I pulled in and let it sit running just to see and it when from strait up and down to 3/4 hot at idle in probably just a few minutes.

With all that said just looking for everyones thoughts before I start buying parts. My buddy thinks I should probably start with a radiator (the coolant looks good didn't loose any either) you could tell they had put some kind of stop leak crap in it even though I don't think it has a leak.

L5wolvesf

You didn't mention if there is any oil/water mix. Assuming there isn't I would check the spark plugs - if 1 or 2 are very clean vs the others that could be where the HG failed. Pictures

Saizer

No oil does not look like there is any mixture of oil and water. Oil looks good coolant looks good, coolant level looks good still. And I will pull all the plugs here shortly. The one we checked was number six which I thought was one of problem ones because of the crossover pipe back there. It seems to run well too, despite the lean code and it wanting to run hot.

kc15842

Well if the head gasket is OK and you changed the thermostat you may want to check the radiator. Does the heat blow hot? Is there a shroud and does it have the lower piece? How about the fan clutch? If the silicone fluid has leaked it may not be functioning correctly.

akwheeler

^^ check the fan clutch and shroud. spin the fan by hand, does it spin really easy/freewheel? if so it's shot. These symptoms are exactly like what I was seeing during my testing on my electric radiator fan install, with the fans off on flat ground at highway speed it runs fine, hit a hill and it gets hot quickly.

Saizer